Coaxial line having helical slots for providing a rotational field capable of being coupled to



Feb. 18, 1964 G. ARLT 3,121,850

COAXIAL LINE HAVING HELICAL SLOTS FOR PROVIDING A ROTATIONAL. FIELD CAPABLE OF BEING COUPLED TO Filed May 27, 1960 2 Sheets-Sheet I 15 LIIIJIR EN IS I COAXIAL LINE A 1 22 23 2o 22' 23' 30 29 j I 31 28 HALL PLATE FOR 24 SENSING CURRENTS m COAXIAL LINE 27 1, 1, l, 26 2s 2s 2s 21.

' 1 FIG. 2 as 32 33 INDUCTIVE I PICKOFF Fla 3 CYLINDRICAL NVENTOR HALL PLATE GOTTFRIED ARLT.

Feb. 18, 1964 G. ARLT 3,121,850

COAXIAL LINE HAVING HELICAL SLOTS FOR PROVIDING A ROTATIONAL FIELD CAPABLE OF BEING COUPLED TO Flled May 27, 1960 2 Sheets-Sheet 2 UHF ANTENNA OMNIDIRECTIONAL lN RING ACTS G, 8 PLANE OF PAPER As DIRECTOR wn'Hou'r AFFECTING DIRECTIONALITY INVENTOR GOTTFRIED ARLT.

BY M A f AGENT Umted States Patent Ofifice meme, i i? 8,

3,121,850 COAXKAL LINE HAVEJG IELHIAL SLOTS FGR PROVIDEQG A ROTATIGNAL HELD CAPABLE OF BEING C(PUPLED T Gottfried Arlt, Aachen, Germany, assigns; to North American Philips Company, Inc, New York, N.Y., a corporation of Delaware Filed May 27, 1960, Ser. No. 32,161 Claims priority, application Germany June 2, 1959 13 Claims. (Cl. 33397) The present invention relates to a device comprising a coaxial line for transmitting signals of very high frequency and/or for obtaining a desired impedance. In this device part of the line circuit is subdivided into a plurality of conductor portions.

The invention has for its object to provide a local inductance, as it were in the coaxial line itself, without interrupting the latter.

The device according to the invention is characterized in that at least part of each of the said conductor portions is helical-1y wou-nd in a given direction around the axis of the line, so that the currents passing through the said parts of conductor portion have a rotational component.

The wound parts of the conductor portions may be arranged in the manner of the spokes of a wheel connecting the external conductor of the line to its inner conductor, or they may be formed by a part of the external and/ or the inner conductor of the line provided with longitudinal slots and axially wound.

In many uses it is advantageous to insulate from each other the wound parts of the conductor portions at the frequency of the signals to be transmitted by longitudinal slots of the external and/ or inner conductor of the line; these slots have a length equal to an odd number of quarter Waves.

The invention will be described more fully with reference to the drawing, in which:

FIG. 1 shows a first embodiment of the invention.

FIG. 2 shows a line terminating device with a Hall disc, which is capable of replacing the coupling winding of the device shown in FIG. 1.

FIG. 3 shows a second embodiment and FIG. 4 shows a line terminating device having a Hall cylinder, which is capable of replacing the coupling winding shown in FIG. 3.

'FIGS. 5 and 6 show a third embodiment and FIGS. 7 and 8 show a fourth embodiment for emitting or receiving high-frequency signals.

The embodiment shown in FIG. 1 comprises mainly a peculiarly shaped end piece of a coaxial line having an external conductor 1 and an inner conductor 2, this line being used for the transmission of signals having a given frequency, for example, of 300 mc./s. The coaxial line 1, 2. is shown in the form of a coaxial cable having inner and outer conductors of circular crosssection, however, the said cross-section might be elliptical or have any other, closed shape. Over a length equal to one quarter wave (h/ 4) or a different odd number of quarter waves, the external conductor 1 is provided with longitudinal slots, so that a plurality of conductor portions, for example eight conductor portions 11-18 are obtained. The end of each of the conductor portions is connected to the inner conductor 2 via a corresponding part of conductor portion 11'-18'. These parts of'conductor portion are located in a plane at right angles to the axis of the cable and are arranged in the manner of the spokes of a wheel, the parts being,'however, all wound in the same, given tangential direction about the axis of the cable, in a helical manner. Owing to the helical shape, the current passing through each of these parts of conductor portion ill-18 has a rotational component in the said plane. These rotational components produce an axial alternating magnetic field, which is capable of inducing a corresponding alternating current in a coaxial coupling winding 19.

In accordance with the structure of an alternating magnetic field, each of the wound parts of conductor portion 11'18 has an appreciably increased self-inductance. Via the h/ 4 conductor portions 11-18, these inductances are connected in parallel. The A/ 4 conductor portions insulate the ends of the wound parts 11'-18 from each other, due to the well-known characteristics of quarter wave line sections (see for example Radar Electronic Fundamentals, Navships 900,016, Bureau of Ships, Navy Department, 1944, at page 330). The longitudinal slots between the conductor portions 11-18 prevent the portion of the external conductor 1 adjacent the wound parts from presenting an inductive short circuit for the wound parts. In the absence of a coupling member as the winding 19, or in case the circuit of this winding is not loaded, the cable 12 is consequently inductively terminated. With a suitable length of the cable 1, 2, this property of the device can be employed for adaptation purposes in high-frequency filters or in high-frequency splitting networks. The device permits in the first place to obtain a simple, easy inductive coupling of a coaxial line with a symmetrical line, or as will be explained hereinafter, with another coaxial line, without any disturbance of the radial symmetry of the line or lines.

An inductive coupling of the coaxial cable with a symmetrical two wire line as shown in FIG. 1. An inductive coupling with another coaxial cable may be obtained, for example, by means of a second device of the type shown in FIG. 1, the two devices being their relative mirror images and the winding 19 of each device being omitted. The ends of the cables are then arranged coaxially, facing each other and the coupling can be adjusted by varying the distance between the respective planes of the wound parts of the conductor portion 11'-18'.

A tight coupling which is, however, not so free of losses, can be obtained with the aid of a Hall disc.

FIG. 2 shows part of a device according to the copending patent application Serial No. 20,284, filed April 6, 1960, having a disc 20 of semi-conductive material, in which the change carriers have a great mobility, the material being, for example, indium-antimony. If this disc is arranged coaxially in the alternating field of the device shown in FIG. 1 and if, at the same time, a magnetic field is applied at right angles thereto, for example, the field of a permanent magnet (not shown) or of an electromagnet excited by means of a direct current an alternating Hall voltage is produced between a central electrode 21 of the disc 26) and the electrode portions 22-29, provided at its outer edge. I

By way of parts of conductor portion 22 29 having a length of one quarter wave or of an odd number of quarter waves, the electrode portions 22-29 are connected to the outer conductor 36) of the second cable, whereas the central electrode 2 1 is connected to the inner conductor 31 of the cable. In this case, also the coupling can be readily adjusted by varying the distance between the outer main surface of the disc 20 and the plane of the wound parts of conductor portion11'-18.

in the second embodiment shown in FIG. 3 a portion of the outer conductor 1 of the coaxial cable 1, 2 is again subdivided by slots into a plurality of conductor portions 32-39. These portions 32-39 are arranged in the form of the spokes of a wheel and bent towards the inner conductor 2 and connect the outer conductor of the cable to the inner conductor thereof. In contradistinction to the first embodiment, these spoke-shaped parts of conductor portion 32-39 are not wound helically; however, the terminal parts 32"-39" of the longitudinally slotted portion of the conductor I are heiically wound.

These parts 32-39" of conductor portion are traversed by currents which also have a rotational component, which produces an axial, alternating magnetic field.

In order to obtain a comparatively strong coupling with these parts of conductor portion with increased inductance, a coaxial winding 40 is preferably arranged around the end of the cable. The coupling can of course be adjusted by displacing the winding 40 longitudinally or by varying its diameter.

An inductive coupling of the device shown in FIG. 3 with a further coaxial cable can be obtained with the aid of a Hall cylinder, the winding 40 being omitted.

FIG. 4 shows part of a further embodiment of the device according to copending patent application Serial No. 20,284, filed April 6, 1960, comprising a cylinder 50 of a semi-conductive material, in which the charge carriers have a great mobility, provision being made of a coaxial cable 51-61 with conductor portions 52-57 and 62-67 of one quarter wavelength of the inner and outer conductors respectively, and with terminal parts 67-67 of the inner conductor portions, a magnet (not shown) producing a radial field across the wall of the Hall cylinder 50.

The device shown in FIG. 3 may, of course, be combined with the Hall disc of the device shown in FIG. 2. A tighter coupling between this device with wound conductor portions and a second cable section is however obtained by arranging the Hall cylinder of the device shown in FIG. 4 in the immediate proximity of the wound parts of conductor portion 32"-39", the cable end 51-61 with the Hall cylinder 50 being arranged coaxially with respect to the cable end 1, 2 with the wound parts of conductor portion.

FIGS. 5 and 6 show a third embodiment, in which the coaxial line 1, 2 is not interrupted and is prolonged by a second undivided section I 2", on the other side of the section subdivided into conductor portions. Between the two undivided sections of the outer conductor 2, 2" this conductor is subdivided into eight portions and each portion consists of a first part 71-78, extending in the longitudinal direction of the cable, of a further helically wound part 71'-78' and of a second part 71-78" also extending in the longitudinal direction of the cable. The length of the unwound parts of conductor portion amounts to approximately one quarter wave at the frequency of the signals to be transmitted and a winding 40 is arranged around the wound parts of conductor portion 71'-78'.

The inner conductor 2, 2 may be solid or hollow and be undivided. As is shown in FIG. 6, it is however subdivided into, for example, four conductor portions, each having a first longitudinal part 81-84, a helically wound part 81-84 and a second longitudinal part 81"-84. In this case the unwound parts of conductor portion again each have an effective length of about one quarter wave at the frequency of the signals to be transmitted. The winding direction of the wound parts 81'-84 may be opposite that of the wound parts 71'-78' of conductor portion of the external conductor 1, 1", so that the rotative components of the currents passing through the parts 81'-84 and through the parts 71'-78 respectively have the same direction. These parts thus operate as small local inductors, included in the cable 1, 2 itself and coupled with each other, so that each amplifies the field produced by the other. The coupling of the winding 49 with the current circuit of the cable by means of the wound parts of conductor portion 7172 is thus reinforced by the coupling by means of the wound parts of conductor portion 81'-84.

In order to obtain a desired impedance in the length of the cable 1, 2 it would of course be sufiicient to subdivide only the inner conductor into conductor portions with helically wound parts. In this case, a coupling winding, if any, for example, as the winding 40, must be arranged around the inner conductor, the ends being externally connected through the external conductor. In this case, the external conductor must, however, be provided with longitudinal slots, in order to avoid an inductive short-circuit.

FIGS. 7 and 8 show a further embodiment suitable for radiating or collecting signals of very high frequency. FIG. 7 shows the device in a sectional view and FIG. 8 in a plan view. The device comprises a conventional coaxial line with an inner conductor 2 and an outer conductor 1, connected to a coaxial, conical line having an inner conductor 91-98 and an outer conductor 101-108, at the apex of the latter. At its face end this conical line can be open (top part of FIG. 7) or closed (bottom part of FIG. 7). The angular aperture of the cone is very large; the angular distance between the outer cone and the inner cone is, as a rule, small. In particular cases the conical line may even be degenerated and formed by two flat, superimposed discs, one of which is connected to the inner conductor of the coaxial cable, and the other to the outer conductor of the coaxial cable. At least one of the cone surfaces, or discs, is provided with spirally wound slots, as i shown in FIG. 8, separating conductor portions 91-98 from each other, whereas the second surface may either have only radial slots or also spirally wound slots, which are however preferably wound in opposite direction with respect to the slots or conductor portions of the other surface. Owing to the spiral led shape of the conductor portions 91-98, a rotational current component is compulsorily produced in the surfaces, which component, in contradistinction to the radial current component, produces a radiation in space. The rotational current components on the circumferences of circles concentric to the conical line have the same phase, so that the aerial exhibits a circular radiation pattern and is suitable for radiating or receiving horizontally polarized waves when the axis of the conical line is in vertical position. The radial current component in the conductor portions does not contribute to the radiation, since it is associated with the line-bound wave of the conical line and is reflected at the end of this line. The mode of operation of this aerial with respect to the circular radiation pattern is the more favourable the larger is the number of spiral led slots or conductor portions.

In order to improve the directional efiect, circular rings or highly conductive material such as the ring of FIG. 8 may be arranged coaxially to the said aerial. If these rings have a radius equal to a predetermined proportion of the wavelength, they can operate as the directors of a Yagi aerial and improve the concentration of the radiation in the horizontal plane, whilst the circular radiation pattern is not altered.

What is claimed is:

1. A coaxial cable comprising an inner conductor and an outer conductor, one of said conductors having an unslotted portion and an adjacent slotted portion, said slotted portion comprising a first portion with slots extending axially of said cable adjacent said unslotted portion, and a second portion adjacent said first portion with helically extending slots that are continuations of the slots of said first portion, the length of said first portion being equal to where N is an odd integer and )t is the wavelength of sig nals applied to said cable.

2. A coaxial cable comprising an inner conductor and an outer conductor, one of said conductors having a slotted portion between a pair of unslotted portions, said slotted portion comprising first and second end portions and a third central portion, the slots of said first and second portions extending axially of said cable, said third portion having helical slots joining the slots of said first and second portions, the length of the slots of said first and second portions being equal to where N is an odd integer and A is the Wavelength of signals applied to said cable.

3. The cable of claim 2, in which said outer conductor is slotted.

4. The cable of claim 2, in which said inner conductor is slotted.

5. The cable of claim 2, comprising means inductively coupled to said third portion.

6. A coaxial cable comprising an inner conductor and an outer conductor, said cable having a portion in which said inner conductor and outer conductor are slotted, said portion extending between a pair of nnslotted portions, said slotted portion having first and second end portions with axially extending slots, and a third central portion With helical slots that join the slots in said first and second portions, the helical slots in the inner and outer conductors having opposite Winding directions, the length of the slots in said first and second portions being equal to Where N is an odd integer and A is the Wavelength of signals applied to said cable.

7. The cable of claim 6, comprising means inductively coupled to said third portion.

8. A coaxial cable comprising an inner conductor and an outer conductor, said outer conductor having an unslotted portion and an adjacent slotted portion, said slotted portion having a first portion with slots extending axially of said cable adjacent said unslotted portion, and a second portion with one end thereof joining said first portion, the slots of said second portion being he'lical and joining the slots of said first portion, and means connecting the other end of said second portion to said inner conductor, the length of the slots in said first portion being equal to Where N is an odd integer and A is the Wavelength of signals applied to said cable.

9. The cable of claim 8, comprising means inductively coupled to the helical portion of said cable.

10. A coaxial cable comprising an inner conductor and an outer conductor, said outer conductor having an unslotted portion and an adjacent slotted portion, said slotted portion having a first portion with slots extending axially of said cable adjacent said unslotted portion, and a second portion With one end thereof joining said first portion, the slots of said second portion being helical and joining the slots of said first portion, said second portion lying in a plan normal to the axis of said cable, and means connecting the other end of said second portion to said inner conductor, the length of said slots in said first portion being equal to where N is an odd integer and )t is the wavelength of signals applied to said cable.

11. The cable of claim 10, comprising means inductively coupled to said second portion.

12. The cable of claim 11, comprising means inductively coupled to said second portion.

13. A coaxial cable comprising an inner conductor and an outer conductor, said outer conductor having an unslotted portion and an adjacent slotted portion, said slotted portion having a first portion with slots extending axially of said cable adjacent said unslotted portion, and a second portion with one end thereof joining said first portion, the slots of said second portion being helical and joining the slots of said first portion, said second portion being a coaxial extension of said first portion, and means separately connecting each separated conductor part 6f the other end of said second portion to said inner conductor, the length of said slots in said first portion being equal to 4 where N is an odd integer and A is the Wavelength of signals applied to said cable.

References Cited in the file of this patent UNITED STATES PATENTS 2,633,532 Sichak Mar. 31, 1953 2,711,439 Smith June 211, 1955 2,859,272 Doherty Nov. 4, 1958 

1. A COAXIAL CABLE COMPRISING AN INNER CONDUCTOR AND AN OUTER CONDUCTOR, ONE OF SAID CONDUCTORS HAVING AN UNSLOTTED PORTION AND AN ADJACENT SLOTTED PORTION, SAID SLOTTED PORTION COMPRISING A FIRST PORTION WITH SLOTS EXTENDING AXIALLY OF SAID CABLE ADJACENT SAID UNSLOTTED PORTION, AND A SECOND PORTION ADJACENT SAID FIRST PORTION WITH HELICALLY EXTENDING SLOTS THAT ARE CONTINUATIONS OF THE SLOTS OF SAID FIRST PORTION, THE LENGTH OF SAID FIRST PORTION BEING EQUAL TO 